The present invention relates generally to electromechanical door openers. More particularly, the invention relates to an apparatus and method adapted for attachment to existing door openers to provide a remote "safety" reversing switch to open to door upon sensing an obstruction in the door path.
The field of electromechanical door operators covers a multitude of applications including pivoting and track mounted overhead doors, and a variety of doors, gates and the like having in common, movement on a single vertical pivot. The door openers generally consists of a motor or other similar power source which provides mode of power through a transmission to urge the door in a selected direction at a selected rate of travel suitable for its particular application. While door openers are generally safe in their operation, there is some danger of a person or an object being caught in the path of a closing door. Many door operators now available include a door reversing or opening mechanism which reverses the travel of the door or opens the door upon sensing an obstruction in the path of the closing door. Such reversers are presently required on all new garage door openers sold for residential uses. While this, over time, will provide the added safety feature to residential applications for garage door openers, it will have no effect of the commercial applications for overhead garage door operators.
There is currently no national requirement for the safety reversing feature to be included on commercial door operators. However, there is presently at least one state requiring safety reversers on commercial overhead door operators. The applicant further believes that this is the beginnings of a national trend which will ultimately require safety reversers be installed on all commercial overhead door operators. Such a requirement would include not only newly installed doors, but also the installation of a safety reverser on existing doors.
Commercial door operators are generally of quite heavy duty construction and have a very long life. The life of a door operator frequently is consistent with the life of the building and often exceeds the life of the building. Costs of replacing the existing door operators that are still functioning to provide the desirable safety reversing feature is very high, and in some cases would be prohibitive.
In light of the trend to require safer commercial door operators, there has been inventive activity in providing door operators that reverse upon sensing an obstruction in the path of a closing door. Most of this activity is directed toward producing a door operator which is reversible upon striking an obstruction and none that I am aware of is available as an attachment or addition to existing door operators to add an economical and easily installed reversing mechanism to the existing door operator.
Generally, the prior art divides into two groups, the first being door operators sensing a load increase on the drive mechanism of the door operator; the second group functioning by sensing the movement of the door and reversing the door operator upon sensing the stoppage of the movement thereof.
The first group of door reversers are exemplified in U.S. Pat. No. 3,719,005 issued Mar. 6, 1973 to Carley; U.S. Pat. No. 4,274,227 issued Jun. 24, 1981 to Toenjes; and U.S. Pat. No. 4,701,684 issued Oct. 20, 1987 to Seidel et al. These patents disclose various methods for sensing the increase in load upon the drive mechanism of the door operator while being closed and communicating that increase in load to the controller to thereby cause reversing of the direction of the door movement. Carley uses a torque switch disposed on its motor output shaft to provide such a result. Toenjes uses the movement of the drive track to actuate a switch responsive to the closing door striking an obstruction. Seidel takes a somewhat novel approach by determining the load indirectly using a temperature sensor disposed in a manner to measure the increase in temperature of the operator drive motor upon striking an obstruction and thereby causing the reversing signals to be sent responsive to the temperature rise.
The second group of door operators are exemplified by U.S. Pat. No. 4,263,746 issued Apr. 28, 1981 to Eller et al.; U.S. Pat. No. 4,376,971 issued Mar. 15, 1983 to Landgraf et al.; and U.S. Pat. No. 4,501,963 issued Feb. 26, 1985 to Parisic. In Eller, door motion is sensed by a flow sensor responsive to an auxiliary pneumatic cylinder. Parisic more directly senses the motion by placing a wheel against the inside of the moving door and generating a stream of electrical impulses therefrom. Upon the cessation of the stream of pulses the device causes a reversal of the door operator. Landgraf provides a series of sensors which are sequentially actuated by passage of the closing door. Therefrom the delay of a sequential pulse indicates an obstruction thereby causing the reversal of the door operator.
All of the above set out examples provide a variety of method and apparatus for reversing a door operator upon sensing an obstruction. They however are drawn to the inclusion of an entire door operator used exclusively on residential applications and none of which are readily adaptable for inclusion upon an existing commercial door operator.